The specific composition of many ceramic compounds can depend upon the character of high temperature environments they are exposed to either during their processing or subsequent use. Thus, for example, some oxides will lose oxygen at high temperatures in neutral and especially reducing environments; the degree of loss varying with the temperature, time, oxygen partial pressure and especially the nature of the compound. Some compounds such as Al.sub.2 O.sub.3 and MgO would show very little or no loss of oxygen under a variety of conditions before overall evaporation or other degradation begins to occur. However, many other compounds will show preferential oxygen loss before loss of other constituents or other major degradations begin to occur. Important examples are materials such as ZrO.sub.2, TiO.sub.2 and SnO.sub.2. If these losses occur in powder forms of the material, normally these can be reoxidized without any deleterious effects. Similarly, if one has a bulk piece of material in which the oxygen loss has been limited, e.g. to very small fractions of weight or density changes, annealing at a sufficient temperature and oxygen pressure so that oxygen can diffuse into the material can bring about reoxidation without problems. However, with more extreme variations from stoichiometry and/or larger sizes, the stresses that result from gradients in stoichiometry during reoxidation can be sufficiently high to cause cracking or total failure of solid pieces of material. Reoxidation has generally not been a significant concern in the past. However, there is increasing interest and work in materials, especially ZrO.sub.2, in which important higher temperature processing is most practically carried out under reducing conditions which can leave the material substantially reduced. Such processing presents serious challenges to successfully oxidizing materials back to their normal oxidization state. Further, these materials, when reduced, may turn black or lose their transparency. Thus, the partiallyreduced form of these ceramics may be useless for many purposes. Throughout this specification and the claims that follow the term "partially-reduced ceramic" means a ceramic which has been reduced to the extent that conventional methods of reoxidation, i.e., heating of the ceramic to a temperature necessary to allow reoxidation, in the presence of a sufficient partial pressure of an oxidizing gas to bring about the desired degree of reoxidation (i.e., the degree of oxidation required for the intended use of the ceramic), causes cracking of the ceramic.